Abstract

Climate change scenarios and their consequences on soil physical quality require a better understanding of soil deformation processes in drying-sensitive soils. This work aimed to analyse the shrinkage behaviour of volcanic, organic, and organic-rich soils in the Southern and Austral Macrozones of Chile, combining laboratory and field measurements. We studied Andosols (6), Histosols (2), and a Cambisol (1) along a gradient of approximately 3500 km from 40(degrees) to 52(degrees) S. Undisturbed soil samples were collected from 2 soil horizons (Hz1: 0-20 cm, Hz2: > 20 cm), and the volumetric soil water content (VWC) was registered at the same depths in different time series between 2007 and 2025. Soil shrinkage curves (SSCs) were measured and fitted to the model created by Peng and Horn (2005) to define the different types of SSCs. The SSCs and the VWC were used to calculate the field (& vartheta;) moisture and void (e) ratios. This combination of laboratory and field measurements provided insights into how: i) moisture and void ratios changed over time, and ii) how different soil shrinkage ranges were reached. This allowed us to better understand how the hydraulic history (pre-drying) could affect soil deformation due to soil drying. In these terms, the studied soils exhibited a large shrinkage capacity (COLE between 0.053-0.885) related to the high levels of soil organic carbon (1.4-30.4%), low bulk density (0.12-1.19 Mg m-3), and water-saturated conditions observed in deeper soil horizons. Soil shrinkage curves presented structural and proportional shrinkage phases consistent with well-structured soils, as well as those that present a high shrinkage capacity. The latter is a major concern regarding more severe droughts and higher hydraulic stress. Therefore, considering future climate change scenarios, the hydraulic history of soils must be considered before using them in agricultural activities (e.g., drainage implementation with no water flow regulation) to avoid their irreversible degradation.